Entities within a glass recycling process stream, such as material recovery facilities (MRFs) and beneficiators, encounter challenges in performing color-sorting and recovering adequate quantities of glass that meet the quality standards for recycled material. A MRF's traditional function has been to serve as a drop-off and sorting point for recycled materials. MRFs sort mixed glass by color into amber, green, and flint glass. Beneficiators typically receive sorted glass from MRFs and then clean and process the glass to make the glass acceptable as source material for bottle production.
However, a quantity of glass is shattered during processing. This by-product of the sorting process is known as mixed cullet, as it is a mix of amber, green, and flint glass shards. Thus, under the traditional processing system, beneficiators amass stockpiles of mixed cullet, which may be used as landfill cover or as a road material (e.g., as a constituent of asphalt). If a beneficiator wishes to extract a higher value from the mixed cullet, the beneficiator is forced to try the difficult and costly task of optically sorting these stockpiles of mixed glass by color.
To date, mixed cullet has thus had only limited commercial use. For example, mixed cullet is typically limited to uses such as an aggregate in paving material, landfill cover, or some similar use. Mixed cullet often is discarded in landfills.
We have discovered that it would be beneficial to develop a process for re-using mixed colored glass, wherein mixed cullet can be used, like color-sorted cullet, in a recycling process to make new glass products. We have also discovered that is would be useful to generate a market for three-color mixed cullet, thereby reducing or eliminating the amount of mixed-color cullet that is discarded.
However, the composition of C3MC from a particular beneficiator varies with time, and the composition of the material from different beneficiators is not uniform. Furthermore, the composition of C3MC may not be accurate to specification. Any difference between a C3MC specification that may be used to manufacture new glass products and the actual composition of supplied C3MC results in substandard glass that is inconsistent with glass manufactured from other batches. Thus, the composition of C3MC from various beneficiators must be known, tracked, and recorded to allow glass manufacturers (also known as “glass plants”) to modify, as may be necessary, the mix of C3MC, as it arrives, with other glass of complementary composition to produce a final blend of C3MC that can be utilized in conjunction with standard processing techniques.
We have determined that it would be useful to provide a system and method for processing post-consumer glass into mixed cullet so that, for example, it satisfies glass manufacturer/plant requirements for purity (e.g., minimal organic, ferrous, paper, plastic and other light fraction, ceramic, and/or aluminum contaminants commingled with the mixed cullet). We have also determined that it would be useful to provide a system and method that uniformly maintains predetermined percentage ranges of amber, green, and flint glass in mixed cullet for a consistent feed stream to glass manufacturers/plants. Providing definite color ranges of mixed cullet ensures that glass manufacturing techniques are changed as infrequently as possible, which increases productivity and reduces cost by, for example, eliminating the need for analysis by the glass manufacturer/plant in order to determine C3MC composition.
We have also determined that it would be useful to facilitate the use of blended C3MC shipped from multiple beneficiators. Glass plants could then advantageously utilize the resulting C3MC blend in conjunction with standard processing techniques to produce new glass products, based upon the consolidation of the various C3MC loads of differing composition.
We have also determined that it would be useful to provide a system and method that provides substantially pure mixed cullet, whereby impurities such as, for example, organic, ferrous, paper, plastic (and other light fraction), ceramic, and/or aluminum contaminants are removed from post-consumer recycled glass.